758 research outputs found
Algebraic lattices achieve the capacity of the ergodic fading channel
In this work we show that algebraic lattices con- structed from error-correcting codes achieve the ergodic capacity of the fading channel. The main ingredients for our construction are a generalized version of the Minkowski-Hlawka theorem and shaping techniques based on the lattice Gaussian distribution. The structure of the ring of integers in a number field plays an important role in the proposed construction. In the case of independent and identically distributed fadings, the lattices considered exhibit full diversity and an exponential decay of the probability of error with respect to the blocklength
Multi-wavelength observations of 3FGL J2039.6-5618: a candidate redback millisecond pulsar
We present multi-wavelength observations of the unassociated gamma-ray source
3FGL J2039.6-5618 detected by the Fermi Large Area Telescope. The source
gamma-ray properties suggest that it is a pulsar, most likely a millisecond
pulsar, for which neither radio nor -ray pulsations have been detected
yet. We observed 3FGL J2039.6-5618 with XMM-Newton and discovered several
candidate X-ray counterparts within/close to the gamma-ray error box. The
brightest of these X-ray sources is variable with a period of 0.22450.0081
d. Its X-ray spectrum can be described by a power law with photon index
, and hydrogen column density cm, which gives an unabsorbed 0.3--10 keV X-ray flux of erg cm s. Observations with the Gamma-Ray Burst
Optical/Near-Infrared Detector (GROND) discovered an optical counterpart to
this X-ray source, with a time-average magnitude . The counterpart
features a flux modulation with a period of 0.227480.00043 d that
coincides, within the errors, with that of the X-ray source, confirming the
association based on the positional coincidence. We interpret the observed
X-ray/optical periodicity as the orbital period of a close binary system where
one of the two members is a neutron star. The light curve profile of the
companion star, with two asymmetric peaks, suggests that the optical emission
comes from two regions at different temperatures on its tidally-distorted
surface. Based upon its X-ray and optical properties, we consider this source
as the most likely X-ray counterpart to 3FGL J2039.6-5618, which we propose to
be a new redback system.Comment: 35 pages, 8 figures, accepted for publication on Astrophysical
Journa
The impact of Basic Fibroblast Growth Factor on Photoreceptor function and morphology
To assess the impact of basic fibroblast growth factor (bFGF) on photoreceptor function and morphology.
METHODS:
Impact was assessed in two models. In one, the endogenous expression of bFGF in photoreceptors was raised by sectioning one optic nerve of rats 3 to 4 weeks before study. In the other, bFGF was injected into the vitreous chamber in rats and cats. Retinal function was assessed from the electroretinogram (ERG), and retinal morphology was studied using DNA dyes, immunolabeling, and in situ hybridization.
RESULTS:
In both models of bFGF upregulation, the ERG b-wave was suppressed over a wide stimulus range and in light- and dark-adapted conditions. The a-wave was not suppressed by either procedure and at the brightest intensities was enhanced by both procedures. In nerve-sectioned eyes, outer retina appeared normal histologically, but levels of bFGF protein in the inner and outer nuclear layers were raised, whereas bFGF mRNA levels remained unchanged. In both models, levels of synaptophysin in the outer plexiform layer and of cytochrome oxidase in inner segments were raised in association with increases in bFGF protein levels.
CONCLUSIONS:
bFGF increased the ability of photoreceptors to respond to light but attenuated the transmission of this response to inner retinal cells, presumably by blocking the photoreceptor-bipolar synapse. If the expression of bFGF protein is upregulated in human photoreceptor dystrophies, it may contribute a reversible component to the loss of vision. The relationship between these actions of bFGF and its ability to protect photoreceptors from stress remains to be established
Rethinking the social impacts of the arts
The paper presents a critical discussion of the current debate over the social impacts of the arts in the UK. It argues that the accepted understanding of the terms of the debate is rooted in a number of assumptions and beliefs that are rarely questioned. The paper goes on to present the interim findings of a threeâyear research project, which aims to rethink the social impact of the arts, with a view to determining how these impacts might be better understood. The desirability of a historical approach is articulated, and a classification of the claims made within the Western intellectual tradition for what the arts âdoâ to people is presented and discussed
The unacknowledged legacy
This paper presents a critical discussion of the treatment of mimetic art, and particularly poetry and the theatre, in the work of the Athenian philosopher Plato (427-347 BC). It centres on Plato's discussion of the corrupting powers of the arts in the Republic, and the implications that his fierce attack on poetry and theatre have for his construction of the ideal polity. The legacy of Platonic ideas in later elaborations of the corrupting power of the arts is discussed. Furthermore, the paper investigates the relationship between current debates on cultural policy and the Platonic idea that the transformative powers of the arts ought to be harnessed by the state to promote a just society. The conclusion thus reached is that âinstrumental cultural policyâ, rather then being a modern invention, was in fact first theorized precisely in Plato's Republic
Determinants of impact : towards a better understanding of encounters with the arts
The article argues that current methods for assessing the impact of the arts are largely based on a fragmented and incomplete understanding of the cognitive, psychological and socio-cultural dynamics that govern the aesthetic experience. It postulates that a better grasp of the interaction between the individual and the work of art is the necessary foundation for a genuine understanding of how the arts can affect people. Through a critique of philosophical and empirical attempts to capture the main features of the aesthetic encounter, the article draws attention to the gaps in our current understanding of the responses to art. It proposes a classification and exploration of the factorsâsocial, cultural and psychologicalâthat contribute to shaping the aesthetic experience, thus determining the possibility of impact. The âdeterminants of impactâ identified are distinguished into three groups: those that are inherent to the individual who interacts with the artwork; those that are inherent to the artwork; and âenvironmental factorsâ, which are extrinsic to both the individual and the artwork. The article concludes that any meaningful attempt to assess the impact of the arts would need to take these âdeterminants of impactâ into account, in order to capture the multidimensional and subjective nature of the aesthetic experience
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MASCOT: an ESO-ARO legacy survey of molecular gas in nearby SDSS-MaNGA galaxies - I. First data release, and global and resolved relations between H<inf>2</inf>and stellar content
We present the first data release of the MaNGA-ARO Survey of CO Targets
(MASCOT), an ESO Public Spectroscopic Survey conducted at the Arizona Radio
Observatory (ARO). We measure the CO(1-0) line emission in a sample of 187
nearby galaxies selected from the Mapping Nearby Galaxies at Apache Point
Observatory (MaNGA) survey that has obtained integral field unit (IFU)
spectroscopy for a sample of ~ 10,000 galaxies at low redshift. The main goal
of MASCOT is to probe the molecular gas content of star-forming galaxies with
stellar masses > 10^9.5 M_solar and with associated MaNGA IFU observations and
well-constrained quantities like stellar masses, star formation rates and
metallicities. In this paper we present the first results of the MASCOT survey,
providing integrated CO(1-0) measurements that cover several effective radii of
the galaxy and present CO luminosities, CO kinematics, and estimated H2 gas
masses. We observe that the decline of galaxy star formation rate with respect
to the star formation main sequence (SFMS) increases with the decrease of
molecular gas and with a reduced star formation efficiency, in agreement with
results of other integrated studies. Relating the molecular gas mass fractions
with the slope of the stellar age gradients inferred from the MaNGA
observations, we find that galaxies with lower molecular gas mass fractions
tend to show older stellar populations close to the galactic center, while the
opposite is true for galaxies with higher molecular gas mass fractions,
providing tentative evidence for inside-out quenching
Radio pulsations from the -ray millisecond pulsar PSR J2039-5617
The predicted nature of the candidate redback pulsar 3FGL\,J2039.65618 was
recently confirmed by the discovery of -ray millisecond pulsations
(Clark et al. 2020, hereafter Paper\,I), which identify this -ray
source as \msp. We observed this object with the Parkes radio telescope in 2016
and 2019. We detect radio pulsations at 1.4\,GHz and 3.1\,GHz, at the 2.6ms
period discovered in -rays, and also at 0.7\,GHz in one 2015 archival
observation. In all bands, the radio pulse profile is characterised by a single
relatively broad peak which leads the main -ray peak. At 1.4\,GHz we
found clear evidence of eclipses of the radio signal for about half of the
orbit, a characteristic phenomenon in redback systems, which we associate with
the presence of intra-binary gas. From the dispersion measure of
\,pc\,cm we derive a pulsar distance of \,kpc
or \,kpc, depending on the assumed Galactic electron density model.
The modelling of the radio and -ray light curves leads to an
independent determination of the orbital inclination, and to a determination of
the pulsar mass, qualitatively consistent to the results in Paper\,I.Comment: 18 pages, accepted for publication on MNRA
No measure for culture? Value in the new economy
This paper explores articulations of the value of investment in culture and the arts through a critical discourse analysis of policy documents, reports and academic commentary since 1997. It argues that in this period, discourses around the value of culture have moved from a focus on the direct economic contributions of the culture industries to their indirect economic benefits. These indirect benefits are discussed here under three main headings: creativity and innovation, employability, and social inclusion. These are in turn analysed in terms of three forms of capital: human, social and cultural. The paper concludes with an analysis of this discursive shift through the lens of autonomist Marxist concerns with the labour of social reproduction. It is our argument that, in contemporary policy discourses on culture and the arts, the government in the UK is increasingly concerned with the use of culture to form the social in the image of capital. As such, we must turn our attention beyond the walls of the factory in order to understand the contemporary capitalist production of value and resistance to it. </jats:p
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